Haptic actuators provide tactile feedback to the user/wearer. In one example, a tactile actuator or “tactor” vibrates a piezoelectric beam to touch the wearer's body. It is hoped that haptic actuators may soon be used to remotely signal and/or command personnel such as military personnel in the field.
Haptic display systems incorporating multiple actuators in an array (vest, garment, seatback, or distributed throughout a handheld device, etc.) driven in a controlled sequence via one or more serially-connected (shift-register-like) elements, referred to as MUXes, for demultiplexing a serial data stream into individual tactor control signals, are known in the art. This approach presents several drawbacks, however. The serially-connected elements create a point of failure in which any actuator positioned downstream of the failure (for example, a broken wire) would cease functioning. This approach also calls for a higher number of wires, since both sequencing data and actuation voltage/waveform must be separately conveyed. This is exacerbated if multiple drive waveforms are required concurrently by different tactors or tactor groups.
Importantly, typical electroactive actuator materials require voltages substantially higher than those typically present in a battery-powered, wearable or handheld system. For example, a typical handheld device may operate from a 3.7 volt rechargeable lithium battery and various subsystems may operate at still lower voltages (1.8, 3.3V). The typical electroactive material requires voltages of 50V or greater (for example, piezoelectric actuators) or even exceeding 1,000V (for example, electroactive polymers).
The presence of such high voltages in the system may present a safety hazard or regulatory hurdles in some market segments. For example, 50 Vp-p is a threshold at which voltages used in a medical device are subject to extra scrutiny and the step-up in regulatory difficulty and IRB approval effort may render a device cost-prohibitive to market or a human trial too expensive to perform. This may be especially true if such voltages must cross the human body and especially the heart, for example, in a wearable haptic vest or other garment. By constraining the presence of electroactive drive voltages to a minimal area and containing said voltages within a self-contained or sealed unit, the safety and regulatory concerns may be reduced or eliminated.